Wayne L. Westcott: Body fat testing is a key to good health

Monday

Nov 28, 2011 at 12:01 AMNov 28, 2011 at 5:32 AM

With the exception of competitive and recreational athletes, most people begin an exercise program to lose weight. Many people live and die by the bathroom scale – which is a poor indicator of personal fitness and physical appearance. Body weight provides an accurate assessment of your total package, but it does not indicate the components that comprise your weight.

Wayne L. Westcott

With the exception of competitive and recreational athletes, most people begin an exercise program to lose weight. Many people live and die by the bathroom scale – which is a poor indicator of personal fitness and physical appearance. Body weight provides an accurate assessment of your total package, but it does not indicate the components that comprise your weight.

Let’s say that you weigh 200 pounds. The scale can’t tell you whether you have 175 pounds of lean weight (muscle, bone, blood, organs, skin) and 25 pounds of fat weight, or whether you have 150 pounds of lean weight and 50 pounds of fat weight. Likewise, let’s assume you reduce your body weight from 200 pounds to 180 pounds. The scale can’t tell you whether you lost 20 pounds of fat (which is desirable) or whether you lost 10 pounds of fat and 10 pounds of muscle (which is undesirable).

A full-length mirror is a much better tool for observing physical changes than a scale as it reveals where you are losing fat and where you are firming muscle.

The body mass index has received considerable attention lately, especially for identifying public school students who have excessive body weight. Typically referred to as BMI, the body mass index is calculated through height and weight measurements placed into a mathematical formula. Unfortunately the resulting number is only as useful as the information provided. Like the bathroom scale, BMI does not indicate the components of your body weight. For example, a 5-foot, 5-inch woman who has 100 pounds of lean weight and 25 pounds of fat weight calculates the same BMI as a 5-foot, 5-inch woman who has 75 pounds of lean weight and 50 pounds of fat weight, because their heights and body weights (125 pounds) are identical. Even though the first woman has only 20 percent fat weight, she receives the same BMI classification as the second woman who has 40 percent fat weight.

Body weight and BMI assessments become even less useful as we age, as non-strength-training adults lose about 5 pounds of muscle every decade. So, if you weigh the same at age 50 as you did at age 20, your BMI would not change. However, you would actually have 15 pounds less lean weight and 15 pounds more fat weight, for a 20-pound difference in your body composition.

To determine changes, it is necessary to have some form of body composition assessment. Most YMCAs and fitness centers can perform at least one of the following techniques for determining your lean weight and fat weight: (1) skinfold caliper measurements; (2) electrical impedance measurements; (3) ultrasound measurements. Each of these assessment methods estimates your percent of body fat. By multiplying your body weight by your percent fat reading you can attain your fat weight. Subtracting your fat weight from your body weight provides your lean weight.

For example, if your body weight is 150 pounds and your body composition reading is 33 percent fat, then you have 50 pounds of fat weight (.33 x 150 lbs) and 100 pounds of lean weight (150 lbs minus 50 lbs). Let’s say you complete a 15-week exercise program and still weigh 150 pounds. If you looked only at your body weight or BMI you would undoubtedly be disappointed, because they would show no change in spite of your exercise efforts. However, if your new body composition reading is 30 percent fat, you would be pleased to learn that you had actually lost 5 pounds of fat (.30 x 150 lbs = 45 pounds of fat weight) and gained 5 pounds of muscle (150 lbs minus 45 pounds = 105 pounds of lean weight) for a 10-pound improvement in your body composition and physical appearance.

As a strong proponent of body composition testing, I would like to see every medical office equipped with appropriate evaluation technology, and to have every annual check-up include an assessment of percent body fat. Knowing how much lean weight and fat weight you have is an important health consideration, as is knowing how your body composition changes on a yearly basis. A pattern of lean weight loss should lead your physician to recommend a sensible strength training program for rebuilding muscle and regaining strength.

With respect to body composition goals, a woman in good physical condition should be between 20 and 24 percent fat, and a man in good physical condition should be between 12 and 16 percent fat. If you are above the desired percent fat level, our research indicates that a basic program of strength and endurance exercise can reduce percent fat readings by more than 3 points after 10 weeks of training.

Wayne L. Westcott, Ph.D., teaches exercise science at Quincy, Mass., College and consults for the South Shore YMCA. He has written 24 books on fitness.

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